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Electrical gremlins

Discussion in 'XJ Technical Chat' started by apato632, Apr 3, 2019.

  1. apato632

    apato632 Member

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    Many thanks in advance.

    - 1983 xj650 Maxim runs awesome.
    - eventually dies.
    - isn’t charging
    - headlight doesn’t work
    - Tachometer needle bobs when signal lights blink at end of ride

    Where would you start?

    I read on here that the headlight and charging system could be related. Like it won’t go on unless the bike is charging?
     
  2. jayrodoh

    jayrodoh YimYam Premium Member

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    That’s sort of correct, the headlight won’t kick on until the stator output is high enough to energize a relay that latches in. If there is something faulty with the AC side of the charging system then that would explain lack of charging and failure of the headlight to turn on.

    Do you have a factory manual? It has a very descriptive test of all the charging system components that should help narrow it down quickly.
     
    Rooster53 and Franz like this.
  3. apato632

    apato632 Member

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    Thanks Jayrodoh,

    I’m currently cleaning all my electrical connections, hoping the solution with present itself.

    I have a Haynes manual but not a factory manual.

    The latest development is that there are two loose, live wires in my headlight housing. One is blue off the main ignition the other is red, off the right hand side wiring harness. There doesn’t seem to be anywhere for them to go. There are also two loose double barrel ground connections.

    Serial number is 5N9-00xxxx (x’s omitted for numbers).
     

    Attached Files:

  4. KrS14

    KrS14 Active Member

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    Have you changed out the old tired fuse panel yet?

    Sounds like you have a very weak electrical system/battery.
     
  5. apato632

    apato632 Member

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    There’s connectivity across all the fuses. The bike runs and runs very well.
     
  6. apato632

    apato632 Member

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    Sorry if this posts twice.

    Latest development is there’s an aftermarket headlight relay? ( (B/w, L/w, R/w, B) located near the horn), replacing with Omron part 4U8-00, marked with blue dot. Is that the right one? Does anyone have a comprehensive list of relays?
     
  7. XJ550H

    XJ550H Well-Known Member Premium Member

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  8. XJ550H

    XJ550H Well-Known Member Premium Member

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    that relay is the side stand relay
    Sidestand (kickstand) Relay:

    Location:
    - on all XJ550 models: left side, onto a welded bracket just behind the rear frame cross tube.
    - on all 1982-84 XJ650 Maxim models: onto a welded bracket outbound of the left outer frame tube, just behind the left coil.
    - on all XJ650RJ Seca models: under the front of the tank, behind the turn signal flasher relay.
    - on all XJ650 Turbo models: on a tab bracket welded to the right frame down tube, below the airbox.
    - on all XJ700 and XJ750-X models: under the left frame side cover, on the plastic regulator-rectifier mounting plate.
    - on all 1981-83 XJ750 Seca models: onto a welded bracket outbound of the left outer frame tube, just behind the left coil.
    - on all 1982-84 XJ750 Maxim/Midnight Maxim models: under the left frame side cover, on the plastic regulator-rectifier mounting plate.
    - on all XJ900 models: under the seat, in the "electrical tray".
    - on all XJ1100 models: under the fuel tank, behind the left side ignition coil.

    Identification:
    - small metal (original) or plastic (replacement) "cube" relay, inked 4U8-00, 4U8-01, or 4U8-02 on the top face.
    - has a blue paint mark or blue locking tab shroud on the bottom of it.
    - normally closed; does not have an internal diode.
    - plugs into a connector shell which has the following set of wires going to it:
     
  9. jayrodoh

    jayrodoh YimYam Premium Member

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    Headlight relay is located under the left side panel, I wouldn’t start chasing that down without doing the charging system tests first. I’ve yet to see a bad headlight relay and I just fixed a Kawasaki Vulcan with same issue, no charge and no headlight.
     
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  10. apato632

    apato632 Member

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    I’m really stumped here guys. I have several xj’s parted down and stored in crates so I can just swap out parts. I’ve done that to,

    - stator
    - rectifier
    - Brushes
    - all relays

    Cleaned the stator with contact cleaner.

    Still no charge.
     
  11. XJ550H

    XJ550H Well-Known Member Premium Member

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    if you look in the link above for relays you will find charging system specs and tests.
    you can ohm out the charging system. low charging is most likely bad brushes in the alternator or poor contact copper rings

    how did the brushes check out when you opened the cover?


    you can also do a diode test on rectifier. diode test diode block the headlight relay uses it.
     
  12. apato632

    apato632 Member

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    Thanks Xj550h,
    I’ve literally swapped out every part, including the rectifier. That I’ve done with three different rectifiers. Same result.

    The brushes looked very long. This bike only has 20,000 km (12,000 miles) on it.

    I’ll check out those tests on the link above. Just frustrating because I can normally just swap out the part for a working one.
     
  13. jayrodoh

    jayrodoh YimYam Premium Member

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    Have you tested any of these parts you swapped out? How do you know they’re working?
     
  14. adrian1

    adrian1 Active Member

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  15. apato632

    apato632 Member

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    Hi all,
    So update is that i have resistance across my white wire connections off the stator coil.

    I don’t have resistance across my green and brown wire off the rotor’s field coil.

    If I touch the brushes against the engine block I get resistance but when I touch them to the alternator rotor I get nothing.

    Any ideas what I should do next? Remove the alternator rotor? Check for grounding?
     
  16. apato632

    apato632 Member

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    Also fun, there was no bolt holding in the alternator rotor. I pulled a bolt off another engine and tried everything again with it properly attached. No change.
     
  17. apato632

    apato632 Member

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    And... I’m hoping this is related to the contact cleaner I sprayed on the copper when cleaning the alternator, but the whole unit smoked when I ran it briefly to check if I was getting charge with higher revolutions. I was not.
     
  18. XJ550H

    XJ550H Well-Known Member Premium Member

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    measure resistance across the 2 copper rings that is what the green and brown wires test does. measure your brushes how long are they?
     
  19. apato632

    apato632 Member

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    I get no reading when I touch both of the copper rings at the same time.

    I’ve got 10cm or just over 3/8 inch of brush.
     
  20. Colin 85 700

    Colin 85 700 Active Member

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    Sounds like your primary winding/armature coil is shot.
    I dont know if you can change that in place but id do that next
     

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